I recently downloaded the trial version of Lightroom 4 onto my new Mac as I couldn't find the CD for Lightroom 3. My trial ended in Lightroom and I didn't export the material I was working on - are the photos lost? I was planning on upgrading to lightroom 4, when I do that will I have to start from scratch or will everything be as I last left it? Also... is it possible to upgrade without having the Lightroom 3 CD? I bought Lightroom 3 on another Adobe account :S

No, activation/ licensing has nothing to do with your user data. It will be just fine once you have revived your LR install. For upgrades al lthat matters is the serial number of the previous product. If you stil lhave it, it would work if not - well, at 150 bucks full price it's still cheap, considering that most cameras or other photographic equipment cost more...